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  1. #1
    Veteran Member Four Rings 20vpower's Avatar
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    1998 A41.8TQMS
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    What will cause the alternator not to charge the battery?

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    OK i need some help bad! This problem is killing me because i cant find the answer. I replaced male ignition switch, alternator, and battery. Battery light still stays on and volts wont go above 12v. I looked in my bentley at the wiring diagrams and the only relay that has anything to do with the starter or alternator is the park neutral postion relay. I pulled it and it didnt seem to be burnt. Should I replace it anyway?
    I just need something solid that I can test. It seems as if im getting nowhere. I just need someone to point me in the right direction. I tested 2 fuses that have anything to do with the ign system and they seemed to be good.
    My starter was hooked up wrong when reinstalling my engine. 1 of the 2 wires that is connected to the solenoid was connected to a stud on the starter. When I started the car, smoke came from the ignition switch and the stud the wire was connected to snapped off from power going through it. I repaced the ignitions switch and notices that the wire from terminal 50 on the ign switch was melted. This wire connects to the D+ side of the alternator.
    Does the ignition switch signal the alternator to send a charge to the battery when the key is on??
    I am completely lost on what could be going on.

    THE best birthday gift I could get today would be someones advice on what is wrong!
    Previously: 12vPower
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    98 1.8tqms MELANGE 50 trimd

  2. #2
    Senior Member Two Rings
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    Apr 09 2007
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    17138
    Location
    stillwater

    Re: What will cause the alternator not to charge the battery?

    i know it sounds elementry but check and double check the battery cables and make sure they are making good connection. other then that i have no idea besides maybe you have a bad alternator again? GL

  3. #3
    Veteran Member Four Rings ghost6303's Avatar
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    Nov 03 2008
    AZ Member #
    34881
    My Garage
    98A41.8TQM
    Location
    CT

    Re: What will cause the alternator not to charge the battery?

    i know its sort of taboo, but autozone or pep boys or wherever tests alternators and batteries for free. might just go and see what they say. with your battery removed from the car, does the voltage read 12.6? it should.

  4. #4
    Veteran Member Four Rings 20vpower's Avatar
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    1998 A41.8TQMS
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    Re: What will cause the alternator not to charge the battery?

    i can go check but its a brand new battery
    Previously: 12vPower
    97 12v fwd CACTUS GREEN (SOLD... thank god)
    98 1.8tqms MELANGE 50 trimd

  5. #5
    Senior Member Three Rings
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    Dec 20 2007
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    23528
    My Garage
    1999.5 Audi A4qm AEB
    Location
    iowa

    Re: What will cause the alternator not to charge the battery?

    It's not the battery, the voltage light is for a no charge or low charge condition from the alternator, have the alternator checked. Yes I read that it's new, but have it checked. You could have a short to a power source in the dummy light circuit if the alternator test fine (which could be very posible with the small electrical fire you had).

  6. #6
    Veteran Member Four Rings 20vpower's Avatar
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    Re: What will cause the alternator not to charge the battery?

    yes im thinking i have a short somewhere like you said. After i test the alternator, how can i try to find the short in the power sorce?
    Previously: 12vPower
    97 12v fwd CACTUS GREEN (SOLD... thank god)
    98 1.8tqms MELANGE 50 trimd

  7. #7
    Veteran Member Four Rings 20vpower's Avatar
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    1998 A41.8TQMS
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    Re: What will cause the alternator not to charge the battery?

    ok i dont know if this means anything, but i traced the wire from the D+ on the alt to where it connects to the wiring harness to check resistance. I got .3 ohm. Then i checked from the wire that was melted to the harness and got .3 ohm. So wouldnt this mean the connection is good? Or am i just a total newb w/ electrical?
    Previously: 12vPower
    97 12v fwd CACTUS GREEN (SOLD... thank god)
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  8. #8
    Veteran Member Four Rings 20vpower's Avatar
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    1998 A41.8TQMS
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    Re: What will cause the alternator not to charge the battery?

    so would B+ be the way the alternator gives the battery power?
    Previously: 12vPower
    97 12v fwd CACTUS GREEN (SOLD... thank god)
    98 1.8tqms MELANGE 50 trimd

  9. #9
    Veteran Member Four Rings Don Supreme's Avatar
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    Jan 25 2006
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    A4 2.0T
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    MD

    Re: What will cause the alternator not to charge the battery?

    ... You have a bad ground... end of story.

    CHECK ALL YOUR GROUND POINTS.

    I just went through this same mess.

  10. #10
    Veteran Member Four Rings 20vpower's Avatar
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    Re: What will cause the alternator not to charge the battery?

    it says its grounded at the battery box. is that the one on the driver side of the engine bay under the coolant res?? or is there one in where the battery is actually at?
    Previously: 12vPower
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  11. #11
    Active Member Two Rings Mecartay's Avatar
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    Sep 12 2005
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    MK1, MK3, 2 B5s, and a B5.5
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    Re: What will cause the alternator not to charge the battery?

    Check and clean your grounds. You may still have something thats connected where it shouldn't be. Ran into a similar problem a couple months ago that wasn't allowing the alternator to charge the battery.

  12. #12
    Veteran Member Four Rings 20vpower's Avatar
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    1998 A41.8TQMS
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    Re: What will cause the alternator not to charge the battery?

    damn i had a dream last night that i had a bad ground. i really hope this is the issue.
    Previously: 12vPower
    97 12v fwd CACTUS GREEN (SOLD... thank god)
    98 1.8tqms MELANGE 50 trimd

  13. #13
    Veteran Member Four Rings 20vpower's Avatar
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    1998 A41.8TQMS
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    Re: What will cause the alternator not to charge the battery?

    Ok checked grounds ( motor mount, under coolant res, at batter box, behind kick panel) all seemed to be intact. I checked alternator (one lead of multimeter to B+ terminal, and one to ground) only gettin 12v.
    Then i checked D+ (one to D+ one to ground) and got 0v.
    Then i checked voltage drop from B+ to positive battery and had 0v....
    So did i get another dead alternator?
    Previously: 12vPower
    97 12v fwd CACTUS GREEN (SOLD... thank god)
    98 1.8tqms MELANGE 50 trimd

  14. #14
    Veteran Member Four Rings 20vpower's Avatar
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    1998 A41.8TQMS
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    Re: What will cause the alternator not to charge the battery?

    I also checked my connections again, 2 connections to B+/30 on starter, 1 white clip to starter. 1 larger red connection to B+ on alternator, 1 small blue connection on D+.
    Previously: 12vPower
    97 12v fwd CACTUS GREEN (SOLD... thank god)
    98 1.8tqms MELANGE 50 trimd

  15. #15
    Veteran Member Four Rings 20vpower's Avatar
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    1998 A41.8TQMS
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    Re: What will cause the alternator not to charge the battery?

    Doesnt the park neutral position relay have a B+ supply to it? That is the only relay that is connected to the starter/alternator. Should i go ahead and replace it or would it not have anything to do with the alternator putting out 12v...
    Previously: 12vPower
    97 12v fwd CACTUS GREEN (SOLD... thank god)
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  16. #16
    Senior Member Three Rings
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    Dec 20 2007
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    1999.5 Audi A4qm AEB
    Location
    iowa

    Re: What will cause the alternator not to charge the battery?

    Did you check the alt.? Aftermarket parts suck.

  17. #17
    Veteran Member Four Rings 20vpower's Avatar
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    Re: What will cause the alternator not to charge the battery?

    checked my original alternator and its still good. im going to replace the wire that goes from the ignswitch to the voltage regulator (D+) on the alternator
    Previously: 12vPower
    97 12v fwd CACTUS GREEN (SOLD... thank god)
    98 1.8tqms MELANGE 50 trimd

  18. #18
    Veteran Member Four Rings Don Supreme's Avatar
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    Jan 25 2006
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    A4 2.0T
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    MD

    Re: What will cause the alternator not to charge the battery?

    The connections to the starter are very important, also a ground under the coolant reso, and of course the nut on the back of the alternator.

    On the passenger side by the motor mount, I believe there are some ground points over there too.

  19. #19
    Veteran Member Four Rings 20vpower's Avatar
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    1998 A41.8TQMS
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    Re: What will cause the alternator not to charge the battery?

    So the ignition switch gives a signal to the alternator to give out a charge when the key is turned on, correct? If so then the fried wire must be the problem. Just finding where it connects is the pita. I hope i have some luck...
    Previously: 12vPower
    97 12v fwd CACTUS GREEN (SOLD... thank god)
    98 1.8tqms MELANGE 50 trimd

  20. #20
    Veteran Member Four Rings arorem's Avatar
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    Mar 24 2008
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    '99 A4 1.8TQ, '74 Triumph Spitfire
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    Illinois

    Re: What will cause the alternator not to charge the battery?

    It could also be the ecu, or smart junction box.

  21. #21
    Veteran Member Four Rings 20vpower's Avatar
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    1998 A41.8TQMS
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    Re: What will cause the alternator not to charge the battery?

    WOW so i replaced the wire(from ign switch to connector in ecu box) with a new one (just soldered on old connectors) abd viola the battery light is off.

    Not to be so excited yet. Went for a cruise around the block and volts started to drop again and then jump back up. Battery appeard on the trip computer but not the battery light... Speedo went dead, gas went dead, etc... now to find the next problem.
    I think im going to swap in the old alt because i had it bench tested and it was fine (14.X v)


    Back to square one
    Previously: 12vPower
    97 12v fwd CACTUS GREEN (SOLD... thank god)
    98 1.8tqms MELANGE 50 trimd

  22. #22
    Veteran Member Four Rings Don Supreme's Avatar
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    Jan 25 2006
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    A4 2.0T
    Location
    MD

    Re: What will cause the alternator not to charge the battery?

    grounds, grounds.

    I had the same issue...... When the grounded got really loose it would drop below 8 volts and everything would cut off and then start again (thank god *lol*.)

    Take a GOOD LOOK at the grounds over on the starter side.

  23. #23
    Veteran Member Four Rings 20vpower's Avatar
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    1998 A41.8TQMS
    Location
    San Jose, CA

    Re: What will cause the alternator not to charge the battery?

    I respect your advice and i hope thats the problem im going to go look again. Its just a pain in the ass that I have to drive this car to work everyday. I really need another daily lol
    Previously: 12vPower
    97 12v fwd CACTUS GREEN (SOLD... thank god)
    98 1.8tqms MELANGE 50 trimd

  24. #24
    Veteran Member Four Rings 20vpower's Avatar
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    1998 A41.8TQMS
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    Re: What will cause the alternator not to charge the battery?

    Ok ok ok, I give up.

    Im taking the car to a shop. I cant find out whats wrong grounds look ok. I replaced the wire going from the ign switch to the harness connecter, then that goes to the voltage regulator in the ecu box after the harness.

    Charged the battery last night to 13v, put it in the car only had 12v. Drove it around last night at just above 12v. Put some loads on it.

    Today after work I start the car and guess what 8v, barely cruise home.... Oh and btw my speedo wasnt working last night at 12v and other gauges were going crazy. My only other guess is that wire fried a bunch of other wires that are wrapped up together coming from the dash/steering column.

    SO now I get to spend a bunch of money finding out what is wrong. YAY HAPPY FRIDAY is all I have to say....
    Previously: 12vPower
    97 12v fwd CACTUS GREEN (SOLD... thank god)
    98 1.8tqms MELANGE 50 trimd

  25. #25
    Veteran Member Four Rings 20vpower's Avatar
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    1998 A41.8TQMS
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    Re: What will cause the alternator not to charge the battery?

    .... didnt end up taking it to the shop, found the problem myself. From the first diagnosis... Something I skipped over. Pinched wire between bell housing and engine lol... Pinched between the single blue connector and the voltage regulator.

    I feel like a jackass. Thanks for everyones help!

    OH and almost forgot now my speedo is working on/off. Least it doesnt count miles...
    Previously: 12vPower
    97 12v fwd CACTUS GREEN (SOLD... thank god)
    98 1.8tqms MELANGE 50 trimd



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